Method of enlarging tube ends



p 1943. A. A. CARLSON ETAL METHOD OF ENLARGING TUBE ENDS 2 Sheets-Sheet 1 Filed June 13, 1940 INVENFOR.

ATTORNEY.

p 1943- A. A; cARLsoN ETAL 6 METHOD OF ENLARGING TUBE ENDS Filed June 13, 1940 2 Sheets-Sheet 2 q Ills- +5 H: g g/5mm. BY W 321 Patented Sept. 28, 1943 METHOD OF ENLARGING TUBE ENDS Arvid A. Carlson, Syracuse, N. Y., and Horace Edmund Karig, Rutherford, N. J., assignors to Carrier Corporation, Syracuse, N. Y., a corporation of Delaware Application June 13, 1940, Serial No. 340,328

' 7 Claims.

This invention relates to a method of enlarging the ends of tubes which bear fins or similar extended surfaces on portions thereof intermediate the ends.

The general object of the invention is to provide a method of and means for providing a tube with a finned surface and belled ends so that when said tube is placed, for example, in an evaporator or condenser it may be readily removed from a tube sheet despite the finned surface. In previous attempts to provide belled ends on finned tubes, it has been usual first to apply a fin of constant dimension upon a tube from end to end and after this operation has been completed the ends were then rolled to a diameter which was equal to or slightly exceeded the diameter of the tubeplus fins, and the fins at the belled ends then removed. This method of belling the ends resulted in tube ends having relatively thin walls which easily cracked or otherwise became damaged when it was attempted to remove such tubes from tube sheets or connect them to tube sheets.

A feature of applicants invention is the provision of a continuous process which not only applies fins to a tube but also enlarges or bells the ends of the tube in a series of consecutive steps, the resulting wall thicknesses of the belled portions being thicker and sturdier than in the case of previous processes. This results in more efiicient operation and in a great reduction of rejected or spoiled tubes, which formerly failed to meet specifications because the belled ends cracked or showed fin marks which prevented a tight joint in a tube sheet.

Applicants utilize a tube of copper or other material which may be subjected to pressure rollers so that fins may be extruded or otherwise produced from the surface of the tube. A mandrel is placed within the tube, the mandrel having portions thereof of difierent diameter, mandrel portions with reduced diameters being arranged to be utilized at the tube ends so that when the tube passes through the machine the walls of the tube ends will be relatively thicker than the walls of the intermediate portions of the tube. The tube ends are then expanded.

This may be accomplished by any suitable means,

such as by swaging, rolling or punching; but regardless of the method employed, a relatively thick wall is obtained compared to that obtained with former processes which produced a fin of the same height throughout the length of the tube. The fins or fin marks at the ends of the tubes, assuming these are produced in a continuous operation, may then be shaved off, whereupon the tube is ready for use. While applicants process produces, in one form of their invention, slight finned surfaces at the ends of the tubes, these are negligible in depth so in effect substantially the original tube wall is available for belling.

A further feature of the invention resides in the provision of a control arrangement for automatically positioning desired ortions of a mandrel at predetermined points Within a tube whereby thicker wall portions are provided at desired points in the tube, as for example at the ends of the tube which it may be desired to enlarge to an overall greater diameter.

One method of carrying out applicants invention will be more apparent from the following written description to be read in connection with the accompanying drawings in which:

Fig. 1 illustrates diagrammatically an arrangement for applying a fin to a tube, a mandrel being inserted as desired so that the walls of the tube may be varied as to thickness at different portions thereof. v

Fig. 2 is a section on the line 22 of Fig. 1.

Fig. 3 illustrates the difference in fin structure at an end of a tube as compared to the fin structure in an intermediate portion, I

Fig. 4 illustrates how the mandrel control operates to provide a thicker wall at a predetermined point in a tube.

Fig. 5 is a fragmentary illustration of a plain tube with a mandrel therein prior to the start of operations.

Fig. 6 shows such a tube with the thicker wall at one end due to the mandrel operation in coordination with the rollers used for finning.

Fig. 7 shows the tube of Fig. 6 after the end has been subjected to belling; and

Fig. 8 shows the finished tube after the slight firming at the belled end has been removed.

Considering the drawings, similar designations referring to similar parts, numeral 9 designates a tube of copper or other material being subjected to the action of rollers on a machine such as that disclosed in U. S. Patent 1,865,575 or German Patent 389,292, dated February 6, 1924. While these patents show means for producing extruded or extended surfaces on a tube, it will be understood that this invention is not restricted thereto but may be utilized as well in other-machines employing rollers or swaging mechanism. Numeral I0 designates a series of rollers suitably rotated to advance tube 9 and simultaneously extrude fins from the surface thereof. Mandrel thereof. The mandrel has an end l3 connected to an arm H which is inserted within opening i5 of stop or limiting device I6. The limiting device i8 is associated with a fulcrum and lever or other linkage shifting device generally designated by the numeral I1. 7

In practical operation, mandrel II is inserted within a tube 8 with the reduced portion of the mandrel l2 at one end of the tube. This reduced portion 12 is of a length sufilcient to provide a desired distance at the tube end which is to have a thicker wall portion. Rollers i0 engage the 'end of the tube thereby advancing tube and mandrel. Simultaneously, the rolling or swaging action compresses the tube wall as shown by numeral I8 in Fig. 6. The fin height at the end,

designated by numeral I9, is relatively negligibler However, when the tube and mandrel have advanced to the point where the thick body portion of the mandrel II begins the rollers will have no further opportunity to compress the metal because the thick portion of the mandrel is substantially snug within the tube. Asa result, fins of the desired height will now be produced. The tube and mandrel will continue to be ad vanceduntil roller thrust bearing 2i contacts stop or limiting device I6. From then on, the

mandrel will be prevented from advancing and the tube alone will be advanced by the rollers for any desired length. When a desired length of full finned tube has been produced, end I8 hits switch 22 which assumes the position shown in Fig. 4. An electrical circuit not shown but readily understood by those skilled in the art, will thereupon be completed and cause arm 23 to change its position from that shown in Fig. 3'

to the position shown in Fig. 4. Through linkage l1, stop I 6 will be pulled in a direction away from the rollers, a prescribed distance which will remove the thick portion of the mandrel H from under the rollers and position the reduced portion of the mandrel l2 under the rollers instead. The rollers will now produce a thick wall with negligible fins as at the other end. While the description has referred to the production of thick walled and negligible finned portions at the ends of a tube, it is obvious that such portions may be provided at any desired points along the length of a tube, depending upon the operation of switch 22 and the related mandrel actuating and stop mechanism.

At the completion of the finning and tube thickening operations, the tube ends may be belied and assume the appearance shown in Fig. 7. While the belling operation may be accomplished by rolling or swaging, applicants punch the ends so that the walls of the tube ends remain substantially as thick as they wereprior to belling, that is, thicker than the wall of the intermediate finned tube portion; In other words, the wall of' the tube ends will be thicker than that of the intermediate portions even though the diameter is greater. To provide the required metal, the operation causes a reduction in the length of the end to make up for the increased diameter as may be noted by comparing Figs. 6 and 7.

While a conventional punching operation will still leave negligible fin heights l9 to be shaved off, in .order to produce the final form shown in Fig. 8, applicants may eliminate this fin shaving operation by providing a form for engaging the outer finned surface during the punching operation to cause the fins by pressure to become part of a smooth outer surface.

It will be apparent that different types of electrical and mechanical means may be employed for shifting the mandrel to desired positions so that portions of lesser diameter will be placed under the rollers. Applicants do not limit themselves to any specific form or arrangement of such devices. Nor do applicants limit themselves with respect to the type of rolling mechanism for advancing the tube and applying a fin thereto simultaneously. While the rollers are designed to provide fins and willwith the specific method described produce-fins of negligible height at the ends, it is apparent that the rollers may be controlled so that no engagement takes place at the tube ends.

Also, under some conditions, a mandrel having a uniform body thickness may be used. In this case, the mandrel would have a diameter substantially equal to the inside diameter of the tube. The production of extruded fins 20 would take place whenever the mandrel is positioned within that portion of the tube desired to be finned whereas the thicker walls i8 would be produced in sections free of the mandrel or from which the mandrel had been withdrawn. Thus, the action of the rollers themselves could be employed to produce the thicker walls with negligible fin surfaces; and the mandrel would be positioned only in those sections where-extrusion of fins 20 from the outer surfaces of the tube is desired. The mandrel plus a connecting rod would be operated as'hereinbefore described to be positioned within specified tube sections, and the advance of the tube beyond a prescribed point could be used to operate the control mechanism for shifting the mandrel, as before described.

Since certain changes may be made in the above construction and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

We claim:

1. A method of producing a finned tube and providing relatively thick walls at enlarged ends thereof, consisting in inserting a mandrel having one portion thereof of reduced diameter within a tube, positioning the reduced portion of the mandrel at one end of the tube, applying pressure engaging means'to the tube whereby the tube and mandrel will be advanced and fins simultaneously extruded from the outer surface of the tube and the tube at said end caused to flow radially to form a thick wall at the tube end, preventing the advance of the mandrel beyond a desired point, continuing to advance the tube for a. predetermined distance, operating a control device when the tube has advanced the predetermined distance and shifting the mandrel responsive to operation of said device to position the reduced portion of the mandrel at the opposite endof the tube, likewise applying the pressure engaging means to the opposite end of the ing having one or more unfinned portions of greater wall thickness comprising, placing a tubular blank upon a mandrel having portions thereof fitting and supporting the wall of the tube, and one or more other portions of smaller diameter spaced from the tube wall, feeding the blank and mandrel axially in intersecting relation to external fin-developing means which exerts radially inward pressure in excess of the resistance of said tubing, whereby fins will be developed and the wall thickness intermediate the same reduced in the portion of the tube supported by the mandrel while the portions unsupported by the mandrel will be radially contracted to avoid fin development, removing the mandrel from the tube, and expanding the contracted portions thereof.

3. The method of forming integral finned tubing having an unfinned end portion of greater wall thickness comprising, placing a tubular blank upon a mandrel for fitting and supporting the wall of the tube but having an end portion of smaller diameter, feeding said tube and mandrel axially in intersecting relation to external fin-developing means which exerts radially inward pressure in excess of the resistance of said tubing, whereby fins will be developed and the intermediate wall thickness reduced in the portion of said tube supported by the mandrel while the end portion will be radially contracted without fin development, removing the mandrel from the tube, expanding the unfinned end portion thereof, and externally finishing said end portion concentric with the inner surface thereof.

4.-In a method of forming integral finned tubing having one or more longitudinal portions thereof unfinned, the steps of internally circumferentially supporting the portion of a tubular blank to be finned against radially inwardly directed pressure leaving the portion not to be finned circumferentially unsupported, and feeding said blank axially relative to external fin developing means which also exert a radially inward pressure in excess of the resistance of the unsupported portion of said blank, whereby the latter will be radially contracted without the development of fins.

5. In a method of forming integral finned tubing having an unfinned portion of greater diameter and at least equal wall thickness to the finned portion thereof, the steps of internally circumferentially supporting a longitudinal portion of a tubular blank against radially inwardly directed pressure leaving another longitudinal portion circumferentialiy unsupported, feeding said blank axially relative to external fin developing means which exert a radially inward pressure in excess of the resistance of the unsupported portion of said tubular blank whereby fins would be developed only on the supported portion, and subsequently expanding the unfinned contracted portion to a larger diameter than that of the original blank. I

6. The method of forming integral finned tubing having one or more unfinned portions of greater wall thickness comprising placing a tube upon a mandrel having portions thereof fitting and supporting the wall of the tube, and one or more other portions of smaller diameter spaced from the tube wall, feeding the tube and mandrel axially in intersecting relation to external fin-developing means which exerts radially in-' ward pressure in excess of the resistance of said tubing whereby fins will be developed and the wall thickness intermediate the same reduced in the portion of the tube supported by the mandrel, controlling the extent of the advance of said tube and mandrel, causing said tube to advance while the mandrel remains in stationary position, and automatically positioning the reduced portions of the mandrel at desired points within the tube so that the tube at said points unsupported by the mandrel will be radially contracted substantially to avoid fin development, removing the mandrel from the tube and. expanding the contracted portions thereof.

7. The method of forming integral finned tubing having one or more unfinned portions of greater wall thickness comprising placing a tube upon a mandrel having portions thereof fitting and supporting the wall of the tube, and one or more other portions of smaller diameter spaced from the tube wall, feeding the tube and mandrel axially in intersecting relation to external findeveloping means which exerts radially inward pressure in excess of the resistance of said tubing whereby fins will be developed and the wall thickness intermediate the same reduced in the portion of the tube supported by the mandrel, controlling the extent of the advance of said tube and mandrel and positioning the reduced portions of the mandrel at desired points within the tube 50 that the tube at said points unsupported by the mandrel will be radially contracted substantially to avoid fin development, removing the mandrel from the tube and expanding the contracted portions thereof.

ARVID A. CARLSON. HORACE EDMUND KARIG. 

